This paper reports the development and experimental validation of a new technique to measure adsorption equilibrium isotherms, based on measuring ZLC desorption curves at low flow rate under carefully controlled conditions. The validity of the method is confirmed by replication of the equilibrium isotherms for representative systems (CO2-CaA, CO2-NaLSX) measured by a conventional volumetric/piezometric method. The new technique has been used to measure equilibrium isotherms for CO2 and other sorbates on a range of zeolitic adsorbents over a wide range of temperature and loading. The data from these measurements are discussed and interpreted in relation to available structural information concerning cation locations in various X-type zeolites.